ICESat-1 Laser Altimeter


NASA Goddard Space Flight Center

National Snow and Ice Data Center

Principal contacts

Dr. Donghui Yi, NASA Goddard Space Flight Center, email:

Dr. Jay Zwally, NASA Goddard Space Flight Center

Data web site


Geoscience Laser Altimeter System (GLAS)


Arctic Ocean

Time intervals

2003-2008 in 15 campaigns, each roughly 33 days long:

Data processing notes

This data set provides measurements of sea ice freeboard and sea ice thickness for the Arctic region. The data were acquired from the Ice, Cloud, and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) instrument, the Special Sensor Microwave/Imager (SSM/I), and climatologies of snow and drift of ice. The data span 15 GLAS campaigns, from 20 February 2003 to 19 October 2008. Data parameters include sea ice freeboard and thickness, in meters, derived from GLAS Release 28 data. The data at NSIDC are provided in three formats: ASCII track data derived from binary track data, binary gridded polar stereographic data derived from ASCII gridded polar stereographic files, and Portable Network Graphic (PNG) image files. The ASCII track data vectors of position and ice thickness have a resolution of about 170 meters in the along-track direction.

The point data for each laser campaign have been averaged for clusters that fall within 50-km grid cells. Summary statistics and probability density functions (PDF) of both freeboad and ice thickness are included here. At least 100 point values are required within a grid cell for the summary to be retained.

Binary gridded polar stereographic data with a resolution of 25 km are also available at NSIDC.

V20140418: updated with 9 new campaigns

Number of samples

15 Laser campaigns, 29,452 clusters, 52,043,216 point values, 8,847,347 km of track


Point data


Yi, Donghui and Jay Zwally. 2010. Arctic Sea Ice Freeboard and Thickness. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.

Zwally, H. J., D. Yi, R. Kwok, and Y. Zhao. 2008. ICESat Measurements of Sea Ice Freeboard and Estimates of Sea Ice Thickness in the Weddell Sea. Journal of Geophysical Research 113(C02S15), doi: 10.1029/2007JC004284.


ICESat and ICESat data processing are fully supported by NASA

Maps of data locations for six campaigns
Period 3d Period 3e Period 3f
Period 3g Period 3h Period 3i

The maps show the locations of point values for each laser period (black dots) and the locations of the 50-km clusters. 100 point values are required to retain a cluster. The colors indicate the mean ice thickness (red is >5 m) for each cluster. The data void at the pole extends to 86 N. Click on a map to see an enlarged version.


Box Plots

ICESat box plots

These are box plots of the ice thickness distributions for each campaign. Only clusters north of 80 N are used to make the campaigns a little more comparable. The median, quartiles, and 5th and 95th percentile values are shown and the star is the mode. The widths of the boxes show the time interval of each campaign.